The nature of the mechanism of insulin control of rat liver glycogen synthase and its converting system will be determined. The effect of alloxan-diabetes in rats on the properties of liver glycogen synthase will be evaluated by kinetic and physical means as a measure of the diabetes-induced alteration of the synthase, and the enzyme's capbility to be regulated by a interconversion system. Insulin control of the synthase phosphatase system, enzymes involved in converting synthase from inactive to active form, will be examined by comparing the capacity for activation of synthase between the diabetic and the normal, and describing the presence or absence of modifiers of the conversion system in the diabetic animal. The rates of synthesis and degradation of glycogen synthase will be compared in the diabetic and normal in order to relate the increase in synthase b observed in long-term diabetes to the effects of insulin on protein turnover. Insulin control of the synthase activity will be evaluated in terms of a hormonal effect on the synthase and activating enzyme, and should provide evidence of the molecular pathophysiology of diabetes.